Study of plasma impurities in JIPP T-II

It has become important recently to study plasma impurities in an actual tokamak machine from the standpoint of the material development for the next-step fusion reactors. In order to study the behaviour of plasma impurities in the tokamak machine, experiments of sampling impurities and analyses of the sampled impurities by RBS and ISS were performed. In the sampling experiments, specimens, which sample the impurities implanted in them during plasma exposure, were set in the scrape-off layer in the JIPP T-II tokamak. Exposed spceimens were then observed by RBS and ISS, and spatial distributions and depth profiles of impurity elements in specimens were obtained. Some impurities, C, O, Fe, Mo, Ta and Ti, were identified in the specimens, and they were considered to originate from residual gases, the torus wall, sample holders and the limiter. From depth profiles analysed by ISS, it was found that most impurity atoms implanted in sampling specimens during plasma exposure are present within a short range of the specimen surface. Our results, as the first attempt, will contribute towards the studied of plasma behavior.